My 2 Year Old An Ear Infection And Was On

My 2 year old an ear infection and was on cefdnir. He then started getting constipated and has been having really hard bowel movements for the last three days, but does have them. We used pedilyte stool softener and that has helped a little. Last night he had a fever that was 101 but went down with Motrin. He woke up with a fever of 99, we did not give him anything and it was normal within a couple hours of him waking up. He has had no fever all day. He winced when trying to eat his lunch and I noticed he had a sore under his tongue. There are no sores anywhere else on his body. He has been eating a lot of clementines the last few days. I just want to know if there could be something serious, or if it could just be a canker sore